The invention pertains to vehicular transport and, more particularly, to methods and apparatus for sensing the position of, and communicating with, vehicles or carriages on a pathway. The invention has application, by way of non-limiting example, in track- or guideway-operated vehicular systems, in warehouse or manufacturing line carriage systems, and in highway vehicular systems. Among the notable features of the invention is the passive nature of the position sensing system, which permits determination of a vehicle""s position (e.g., by a wayside station) without requiring a source of power on the vehicle itself.
The prior art proposes a number of methods for determining vehicle position. For example, U.S. Pat. No. 6,005,511, for a highway vehicle guidance system, issued Dec. 21, 1999, suggests using radar signals to interact with stripes in the highway; see also, U.S. Pat. No. 6,008,552, issued Dec. 28, 1999, and U.S. Pat. No. 6,034,499, issued Mar. 7, 2000.
Such prior art systems require a battery, generator or other power source on the vehicle, e.g., to support the on-board generation of signals that directly or indirectly indicate its position and that are transmitted to a wayside station, to another vehicle, or the like, for interpretation. While on-board power is available in many cases, it is often not. This is particularly true, by way of non-limiting example, with smaller vehicles such as are used for material handling systems and for thrill rides.
Regardless of whether such vehicles have a convenient source of on-board power, there are typically stringent demands for sensing their positions precisely. In some cases, vehicles operating with headways of one second or less have been proposed. Without accurate, up-to-date position information, safe operation can be jeopardized.
A variety of methods have been used in the prior art to enable communication between a vehicle and the wayside. Most of these involve the use of wireless radio communications. One disadvantage of such schemes is signal degradation from intervening structures such as buildings and tunnel walls. Another disadvantage is their requirement for on-board energy, which may be unavailable in unpowered vehicles.
A common use of vehicle-to-wayside communications is the transmission of vehicle identifications, typically, vehicle ID numbers. The prior art has proposed some options for this which do not require on-board electronics or on-board power. These typically call for labeling the vehicles with bar codes, or the like, and detecting those codes with readers disposed at wayside. Unfortunately, such solutions are expensive and subject to improper operation, e.g., due to accumulation of dirt or other environmental factors. While less expensive solutions have been proposed, they still often fall victim to environmental factors.
In view of the foregoing, an object of the invention is to provide improved methods and apparatus for pathway-based position sensing and communication.
Another object of the invention is to provide such methods and apparatus as can be applied to sensing the positions of, and communicating with, vehicles operated on or in conjunction with a pathway.
Yet another object of the invention is to provide such methods and apparatus as can be applied to all types of vehicles, regardless of whether they travel over rail, road or other mediums.
Yet still another object of the invention is to provide such methods and apparatus as permit vehicle detection and communication, e.g., regardless of whether the vehicle is underground or otherwise obscured from contact with a ground station antenna or satellite.
The foregoing are among the objects attained by the invention, aspects of which provide a position sensing system that generates a vehicle position signal in one or more sensing windings, e.g., for detection by a wayside controller. The system is advantageous in that it requires no power source on board the vehicle, i.e., the vehicle can be xe2x80x9cpassive.xe2x80x9d
According to one aspect, a system according to the invention includes a flux or field source and one or more sensing windings disposed along a pathway. A transducer (or other coupling element) is configured to couple energy from the source to the sensing winding(s) to induce therein a signal that varies with the position of the coupling element along the pathway.
The pathway can be a highway, railway, guideway of a linear motor system, or any other vehicle or carriage way. The flux source may be provided by one or more transmission windings that are disposed along that way. Such transmission windings, which can be actively powered in order to provide local magnetic field flux, are preferably disposed with respect to the sensing windings such that little or no net signal is coupled between them, e.g., except in the proximity of the coupling element.
According to further aspects of the invention, the coupling element is carried on a vehicle, carriage or other object whose position along the pathway is to be determined. The coupling element can be a passive structure, such as a simple body of ferromagnetic material, of conductive material, or of a combination of both. It may also comprise one or more receiver loops that are tuned, e.g., with a capacitor or other element, to resonate at a frequency of a signal generated by the transmission winding or other flux source.
According to related aspects of the invention, the sensing windings have a spatial configuration that localizes or varies their reception characteristics vis-a-vis energy coupled from the transmission winding(s). As a consequence, the form of the position signal generated in a sensing winding varies in dependence upon where the transducer or other coupling element is positioned.
In related aspects, the invention provides systems as described above in which one or more sensing windings are arranged as a series of loops of alternating sense. Movement of the coupling element over the loops induces position signals with envelopes that vary with position and that have periodic nulls or dips.
Still further related aspects of the invention call for use of a transmission winding with loops that are disposed at a period that is a multiple or sub-multiple of the period of the sensing loops. Alternatively, or in addition, the transducer can have a width (or other dimension) in the direction of the pathway that is a multiple or submultiple of the transmission winding loop and/or sensing winding loop periods.
Thus, by way of non-limiting example, the period of the transmitter loops may be twice that of the sensing loops, and so forth. This can be effective to provide an induced position signal envelope with well defined nulls or dips and, otherwise, with a definite envelope form as the transducer moves along the pathway. Preferably, two offset sensing windings are employed to provide phased signals that may be combined for enhanced position resolution.
An advantage of a system according to the aforementioned aspects of the invention is that it can eliminate the need for powered electronics on-board the vehicle, carriage or other object whose position is being determined.
In cases where on-board electronics may be required, power can be derived from the signal in the transmission winding without the need for a permanent storage unit (e.g., battery) or other power source. To this end, further aspects of the invention call for systems as described above in which a tuned receiver loop is utilized as a coupling element to inductively transfer power to the vehicle.
According to related aspects of the invention, circuitry is provided for effecting communications to/from the vehicle on the pathway. For example, a receiver loop as described above can be utilized to receive a command signal sent to a vehicle on the pathway by the wayside controller. Such a loop can also be utilized to send information. By way of example, the coupling effect of the tuned receiver loop can be varied (e.g., by lowering the Q of the tuned circuit) to encode a communication signal xe2x80x9con top ofxe2x80x9d the position signal in the sensing windings. This aspect of the invention can be utilized by a vehicle in order to send its identification number, or ID, to a wayside controller. The allows one-way or two-way communications without requiring a battery or other power source on the vehicle.
Still further aspects of the invention provide systems as described above in which the transmission and sensing windings are disposed among stator motor windings of a linear motor. Advantageously, the period the transmission and sensing winding loops, and the width of the transducer, can be selected to avoid interference from the stator motor windings and to couple clear signals.
The foregoing and other aspects of the invention are evident in the drawings and in the description that follows.